Targeted prostate biopsy using magnetic resonance imaging-ultrasound fusion

摘要

Prostate cancer is the second most common cancer among men worldwide, with an estimated 1.1 million new diagnoses and over 300,000 deaths reported in 2012 by the World Health Organization. A recent 5-year prevalence of the disease was nearly four million, far exceeding all other malignancies in men.1 Because of these numbers, efforts to improve early detection, accurate assessment of disease burden, and appropriate treatment options are important public-health priorities. However, the basic tool for diagnosis, transrectal ultrasound (TRUS) guided biopsy, is flawed by failure to detect many serious cancers (>30% false negative rate)23 and over-detection of nonserious cancers. Multiparametric magnetic resonance imaging (mpMRI) of the prostate empowers the clinician to identify tumors that would otherwise be missed by conventional techniques and to record the precise locations of positive cores through targeted biopsy using MRI-ultrasound (MRI-US) fusion. As mpMRI advances and the level of experience for the user grows, the correlation between the level of suspicion for a prostate lesion and the MRI-US fusion targeted biopsy revealing malignancy improves. Consequently, the concordance among the targeted biopsy and surgical pathology rises. This in turn, allows the patient and provider to be confident that the therapeutic plan decided upon is representative of the true disease state. TECHNIQUE Various predictive tools and tests have been utilized to help urologists counsel patients regarding the need for a prostate biopsy, as well as the potential aggressiveness of their disease. Renditions of prostate-specific antigen (PSA) that help counsel a patient on forgoing or obtaining a biopsy include PSA density, PSA velocity, Free PSA %, and Prostate Health Index. Lately, genetic testing has emerged as an additional option in the urologist's armamentarium. Hologic's Prostate Cancer Gene 3, Myriad Genetic's Prolaris and Genomic Health's Oncotype Dx are genetic tests that examine the urine or prostate biopsy tissue to help delineate the potential aggressiveness of the disease. Technology has also paved the way for improved prostate imaging with the hope of defining benign or malignant changes in patients undergoing prostate cancer screening and to track the areas of concern over time. Techniques have included variations of US, computed tomography, MRI, as well as positron emission tomography imaging.4 Regardless of imaging choice, the goal is to extend beyond the limitations of blind biopsy for those at risk, by detecting more clinically relevant cancers, identifying the location of these cancers, decreasing patient morbidity, and aiding in the development of a safe and effective treatment plan. Multiparametric magnetic resonance imaging has become the imaging of choice by many practitioners including the urologic surgeon since the advent of the 0.35 T magnet.5 Now, diffusion-weighted imaging (DWI), dynamic contrast-enhanced (DCE), and spectroscopic imaging have supplemented the simple T2-weighted imaging (T2-WI) to improve cancer detection as well as staging.6 mpMRI compared to standard 12 core biopsy has been shown to increase the number of positive cores, men diagnosed with more than 1 core, and proportion of men diagnosed with clinically relevant prostate cancer.7 Preoperative/preprocedural counseling, active surveillance (AS) monitoring, and intraoperative planning rely on the capability of mpMRI. However, biopsy remains the gold standard at diagnosing prostate cancer despite available imaging, blood and genetic testing. It is up to the provider how the tissue is obtained and how mpMRI can be incorporated into this process. Three different methods have been described in order to perform a targeted prostate biopsy by fusing MRI: MRI-MRI fusion (also called in-bore biopsy) and MRI-US fusion which includes both device and cognitive fusion. In-bore biopsy implies the patient is physically in the MRI tube obtaining his biopsy. Despite the